In ∆ABC, DE is drawn parallel to BC, cutting AB and AC at D and E, respectively, such that AB = 7.2 cm

(b) 4 cm

It is given that DE∥">∥BC.

Applying basic proportionality theorem, we get:

$\frac{A D}{A B}=\frac{A E}{A C}$

$\Rightarrow \frac{4.5}{7.2}=\frac{A E}{6.4}$

$\Rightarrow A E=\frac{4.5 \times 6.4}{7.2}=4 \mathrm{~cm}$